1. Field of the Invention
The present invention relates in general to gantry tools and, in particular, to reconfigurable precision gantry tools and reconfigurable tooling systems for performing tooling operations on workpieces and assembling structures.
2. Related Art
The precision machining of large workpieces requires the use of a wide array of expensive machine tools such as full size models and gauges, templates, fixtures, drill hoods, and drill-sets. These tools have a substantial acquisition and maintenance costs, as well as costs related to their storage, property management, inspection, reinspection, and accountability. In addition, the manufacturing tolerances and repeatability achievable with these tools is limited.
For example in the aerospace industry, large airframe components such as fuselage sections can be precision machined only with the use of very costly full size models and gauges.
A typical series of models needed to drill precision holes is shown in FIGS. 1A-1B. As shown in FIG. 1A, the first step in this process is to fabricate a male master model 100 of a fuselage section, which model is made of metal or plaster and has projections 105 of the size and at the locations required for the holes to be drilled in the fuselage section. A female plaster cast 110 is formed over the model 100, which cast has apertures 115 formed over the projections 105.
As shown in FIG. 1B, a male cast back 120 is formed from the plaster cast 110, which cast back is also made from plaster. Again, projections 125 are formed by the plaster flowing into the apertures 115 in the cast 110 of FIG. 1A. Finally, a drill bonnet 130 made of a composite material, such as fiberglass or graphite composite, is formed over the cast back 120. The bonnet 130 has apertures 135 of the correct size and at the correct locations where holes are required to be drilled.
The first step in using the bonnet 130 is to fasten a fuselage section into an assembly jig using bracing means, or "details", and locator pins to provide a reference position for the fuselage. The bonnet 130 is then secured adjacent the fuselage section and aligned with the section using the locator pins. The bonnet 130 then serves as a drilling template through which holes are drilled into the fuselage section. It should be noted that FIGS. 1A and 1B are basic drawings and show only a few holes for simplicity. An actual bonnet will have hundreds and possibly thousands of holes.
As such, the cost to fabricate a typical drill bonnet 130 can average $1 million and take from 1 to 12 months. As an example, fore F-18 aircraft, 900 bonnets are needed to drill all the fuselage holes. Thus, the total cost for the drill bonnet tool family for the F-18 is approximately $1 billion. Full scale interior models, called master gages, are also required to precisely locate and drill holes in details which are attached to interior structures of the assembly jig. These details are used to locate bulkheads, frames and ribs of the aircraft. Such master gages can cost between $5-10 million each and the F-18 requires 33 such master gages, for a total master gage tool family cost of approximately $250 million. In addition, new master models and gages need to be fabricated for either a new aircraft component or changes to an existing one, requiring from four to 24 months to prepare.
Therefore, what is needed is a device that eliminates the need for costly tool families, such as drill hoods, master models, gauges and facility mixtures. What is also needed is a device that is inexpensive and is made from standardized parts to reduce cost and fabrication time. What is also needed is a device that is reconfigurable and for custom tooling operations. Further, what is needed is a device having a leveling mechanism with a programmable memory to improve accuracy of hole location and to allow repetitive tooling operations.
Moreover, the large assembly jigs, large drill bonnets, drill tools, and drill hoods discussed above are used to assemble an entire structure, such as an aircraft. This process is referred to as a fixed custom matrix. This is because each different workpiece, no matter how slight the difference, must have its own custom assembly jig since the jigs are not reconfigurable. In this painstaking and expensive process, for each custom jig, tooling operations are performed only one workpiece at a time. Expensive work stands are elevated above the ground and are built around each custom assembly jig to allow workers to perform tooling operations on the workpiece. As a result, the expensive custom assembly jigs are the building blocks of the structure to be built. Consequently, this technique is very expensive, inefficient, and wastes resources.
Therefore, what is needed is an apparatus and method for assembling large structures without fixed custom matrices. What is additionally needed is a new assembly line with reconfigurable tools for assembling large structures. What is further needed is a new assembly line which uses the workpieces that comprise the final structure as the building blocks of the final structure and not the custom assembly jigs.
Whatever the merits of the above mentioned systems and methods, they do not achieve the benefits of the present invention.